微型钢管桩加固既有基础变形特性现场试验

依托河南理工大学锅炉房既有基础加固工程,优化微型钢管桩群桩加固既有基础的施工步骤,将既有灌注桩基础与柱身简化为一端固接一端简支梁模型并验证其准确性; 开展微型钢管桩加固既有基础变形特性现场试验,测得微型钢管桩群桩施工过程中既有柱子和两柱之间的地表位移以及柱子角度的变化规律,比较顺逆结合和单一逆时针群桩施工顺序对既有柱子以及地表位移的影响,探讨加固施工过程对既有上部柱子结构的变形(位移、倾角)机理。结果表明:顺逆结合的群桩施工顺序相对优于单一逆时针压桩顺序,地表位移最大值可以减少约50%,顺逆结合或单一逆时针施工顺序引起的地表位移最大值分别为既有上部柱子位移的1/6和1/4; 先施工的微型钢管桩会对周围土层产生一定的遮帘加筋作用,后施工桩朝此方向造成的土体扰动和位移相对减小,从而减小了微型钢管桩施工对既有上部柱子结构的影响; 2种施工顺序试验条件下,位移与应力最大值一般出现在第3根桩或第4根桩施工过程中。

Field Test on Deformation Characteristics of Existing Foundation Reinforced by Micro Steel Pipe Pile

Based on the existing foundation reinforcement project of Henan Polytechnic University boiler house, the construction steps of the existing cast-in-place pile foundation reinforced by the micro steel pipe pile group were optimized, and the foundation and column were simplified as a beam model fixed at one end and simply supported at the other, then its accuracy was verified. The field test on the deformation characteristics of the existing foundation reinforced by the micro steel pipe pile was carried out. The surface displacement between the existing column and two columns and the change law of the column angle were measured during the construction of the micro steel pipe piles. The influences of construction sequence with the combination of clockwise and counterclockwise and single counterclockwise pile group sequence on the existing columns and surface displacement were compared. The mechanism of the deformation(displacement and inclination)of the existing upper column structure during the construction of the micro steel pipe piles was discussed. The results show that the pile group construction sequence with the combination of clockwise and counterclockwise is better than that with the single counterclockwise pile, and the maximum surface displacement can be reduced by about 50%. The maximum surface displacements caused by the combination of clockwise and counterclockwise and the single counterclockwise construction sequence ares 1/6 and 1/4 of the displacement of the existing upper column, respectively. The first construction micro steel pipe piles will have a certain effect of shielding and reinforcing the surrounding soil layer, then the soil disturbance and displacement caused by the post-construction piles in this direction are relatively reduced, so the influence of micro steel pipe pile construction on the existing upper column structure is also reduced. Under the two construction sequence test conditions, the maximum displacement and stress generally appear in the construction process of the third or fourth pile.